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Cisco IOS vulnerable to DoS or arbitrary code execution via specially crafted IPv6 packet

Vulnerability Note VU#930892

Original Release Date: 2005-07-29 | Last Revised: 2005-08-02


Cisco Internetwork Operating System (IOS) IPv6 packet handling is vulnerable to a denial-of-service attack and may potentially be vulnerable to a flaw that allows arbitrary code execution.


Cisco Systems devices running IOS that are configured to handle Internet Protocol version 6 (IPv6) traffic may not properly handle a specially-crafted packet sent from the local network segment. This improper packet handling may result in a denial-of-service condition or in the execution of arbitrary code on the device running IOS. The specific nature of the crafted packets exploiting this vulnerability is not known.

Only devices configured to handle IPv6 traffic are vulnerable to this flaw. Any logical or physical interface that handles the crafted packet is vulnerable to the flaw. In addition, the attacker must send the crafted packet on the local network segment. Packets sent one or more hops away from the device will not affect the vulnerable device in a negative manner.


A remote, unauthenticated attacker on the local network segment that can craft and send an arbitrary IPv6 packet may be able to crash or take control of the device running IOS.


Apply An Update
For details on fixes, updates, and workarounds, please see Cisco Security Advisory 65783: IPv6 Crafted Packet Vulnerability.

Apply Workarounds

Disabling the handling of IPv6 traffic eliminates exposure to the vulnerability. This is accomplished with the "no ipv6 enable" and "no ipv6 address" commands for each interface.

Vendor Information


Cisco Systems Affected

Updated:  July 29, 2005



Vendor Statement

Cisco Systems, Inc. has released a security advisory regarding a vulnerability which was disclosed on July 27, 2005 at the Black Hat security conference. Security advisory is available at:

For up-to-date information on security vulnerabilities in Cisco Systems, Inc. products, visit

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


US-CERT has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

CVSS Metrics

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Information regarding this vulnerability was primarily provided by Cisco Systems, who in turn acknowledge the disclosure of this vulnerability at Black Hat USA 2005.

This document was written by Ken MacInnis.

Other Information

CVE IDs: None
Severity Metric: 25.64
Date Public: 2005-07-27
Date First Published: 2005-07-29
Date Last Updated: 2005-08-02 23:12 UTC
Document Revision: 26

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